We plan to study the structure and function of ribosomal RNA and ribosomes, as well as related RNA such as messenger and transfer RNA. We shall continue to concentrate on comparative studies involving mitochondrial and cytoplasmic protein-synthesizing systems, and the mRNA that programs these systems, both in normally growing animal cells and in cells infected by the alphavirus Sindbis. Samples labeled with radioactive methionine, phosphate and/or uridine will be obtained from insects as well as mammalian cell cultures. They will be subjected to general sequence analysis, and also to analysis of minor (especially methylated) nucleotides, and of 5'-termini, in particular. Methodology will include alkaline, acid, and enzymatic digestion; paper electrophoresis and chromatography; and DEAE cellulose and boryl sephadex column chromatography.